Preparation of cyanogen compounds



Sept. 2o, 192i. 1,642,694

R. w. POINDEXTER, JR., ET AL lPREPARATION OF CYANOGEN COMPOUNDS Filed Aug. 19. 1926 31a/wanton Patented Sept. 20, 19727.

UNITED STATES` PATENT'oFFIcE.

ROBERT W. POINDEXTER, JR., OF LOS ANGELES, AND ILLIAIVI EARL OLBERG, 0F LONG BEACH, CALIFORNIA, ASSIGNORS TO CALIFORNIA CYANIDE COMPANY, IN"- CORPORATED, OF NEW YORK, N. Y.` A CORPORATION OF DELAWARE PREPARATION CYANOGEN COMPOUNDS.

Application led August 19, 1926. Serial No. 130,360.

This invention relates to the production of cyanides, and particularly to an improved p rocess for the production of cyanide of calclum.

In United States Letters Patent No. 1,573,732, Metzger has described a process of producing cyanides such as calcium cyanide 1n a dry and concentrated form. This process depends upon a reaction between calcium carbide and hydrocyanic acid proceeding as follows:

The product contains a variable proportion of hydrocyanic acid of combination but so far as has been determined there are usually during the reaction. The water acts apparently as a catalyst and only a small amount is required to ensure that the reaction `will proceed with Acomparative rapidity. The water can be introduced with thev hydrocyanic acid or otherwise. Thus, a bone dry calcium cyanide should be treated preferably with hydrocyanic acid containing'from onehalf to live per cent of water calculated on the weight of` carbide employed. The presence of a surplus of water in the reaction as described is undesirable owing to the tendency of the water to cause partial polymerization.

It is the object of the present invention to avoid the necessity for adding water in conducting the reaction between calcium carbide and hydrocyanic acid and to provide a proc ess capable of producing improved yields of y the desired product and to otherwise sim-1 plify the operation. i y

Other objects and advantages of the inven tion will be apparent as it is better under- `stood by reference to the 'following specifi` cation and accompanying drawing in which an apparatus for use 1n carrying out the 1nvention is illustrated dlagrammatlcally.

l/Ve have discovered that the reaction between calcium carbide and hydrocyanic acid can be catalyzed or otherwise accelerated by the addition of substances which may be re .ferred to as promoters `to the mixture duri ing the reaction. Various 4substances act as promoters of the reaction and among them we tindthat the' following are best adapted to the accomplishment of the desired object: Ammonium bromide, calcium bromide, am momum thiocyanate, zinc bromide, ammonium iodide, zinc chloride and benzoic acid. The capacity'of theseveral substances mentioned lto promote `the reaction varies and the proportion thereof required in con-- ducting the reaction is subject likewise to variation. As examples of the proportions which may be desirable we find that from twoto eight per cent of ammonium bromide or from one and one-halfto five per cent of 'f ammonium thiocyanatewill` ensure the rapid and effective reaction between calcium carM bide and hydrocyanic acid. 7e have also discovered that mixtures of the promoters mentioned may also be used with advantage, for example,'a `mixture containing from two to five per cent of ammonium bromideand from one-half to two per cent of ammonium thiocyanate. The percentages mentioned are based upon the weight ofthe carbide employed. Y

If the calcium carbide is free from con taminating constituents substantially pure calcium cyanide can be produced. Since,

however, calcium carbide of a commercial f grade is rarely pure, calcium cyanide produced therefrom will containy certain impurities.' It is possible, nevertheless, to produce a very high grade of calcium cyanide from good commercial calcium carbide. Such a carbide contains approximately of calcium carbide and it can be made to yield aproduct containing cyanogen equiva lent to one hundred 'or more per cent of calcium cyanide. t

In carrying out the reaction it is desirable to employ calcium carbide in a finely divided state. 7e have found that carbide of from forty to one hundred mesh or even finer is suitable for the reaction. `It is not essential however, that the calcium carbide be introduced in a pulverized condition. Carbide 1n lump form can be used provided that it is stirred sufficiently during the reaction to eX- pose fresh surfaces continuously to the action of theV hydrocyanic acid. The resultant abrasion will remove" the calcium cyanide from the lumps and thus permit the continued; attack.. of; the hydrocyanic acid. upon the. carbide.

The preferred,v apparatus... comprises. a. re-.. action vessel having suitable means to permit cooling or heating as desired-.fi The ves'- sel which should be closed mayYK haveinletsy to permit the introduction ofthew'calciurn Carbide and.. liquid hydrocyanic acid and ShOuldfbe pioviidecl, Witlifsi'trng. t0 maintain. suene.' agieren'. of. the. materia duringtlien ion. -Qllllegtolthe.factthat; 011e.' @tithe real ien-Producten,lgasepus acct.: ylen'e. t- `s n'elesa'ryA teV have. an.. Outlet; for. the gas.k V certainramou'nt of hydrocyanic acid lasfvapor. will' befcarriedY off' by, the gals.

and' 'this b cenrlesed. and', returned t.

the reaction vessel.;l The acetylene vsliozuldfbe;

scrubbed toV remove any lh'yfdrfocyanic' acid which ifs not' 'condensedl It cany bezf used thereafter for; ofjthe' purposes for whichacetylene;iseniployefdf. i t i i The reaction cank be carried`I` out, likewise Il afClQSf.. allretu Slcmll rf t0] a Clough. mixer. in which l the calcium ,carbide isfplacedV and! into` which the: hydrbcyanic acid islsupplied.atlalirateiiltsulentterreni? reactiou'-with, thecarbidek lnfthiscaee they materialwould. be sub,StuntiallyA dry. during n the` entirev 'operation'Y .fthefnecessity for. drying, thfeproduct- Vwouldfbefavoided.;v Siml.

bide continuously. and" to .apply hyd-lllil@ acid' thereto `ou thecounter-'current principlef son `that the partially., Acompleteds product WQulClbe .Caused fb, reallvlfhja .feh Ser-ply l of liquidf hydrocyanic". ac'idlwhile the lfresh calcium carbide would combine With that@r portion. of the hydrocyanic acid.which es the` .'qiiality, of; the.. calcium, .carbide fused..

Referringtd. the drawing@ in whichVU the y preferred apparatus; isiillustrat.ediV 5. indi- Cates al.reaction.i vessel. having a jaicketr through *which heatingl and .cooling l agents,

e' canfbecirculatedafs-desired The Vessel isz. provided preferably with al hinged.;bottomsV 7 vvlliiclnis-` normally.y secured iin. closed posif ti on..l by.. hingI can be dropp'e readily? @discharge the con-l.

, tents .of thelves'sel clamp bolts S., The bottomof calcium carbide and is connected to the vessel 5 by a conveyor 10 having a screw 11 therein. A pipe 12 permits the introduction of liquid hydrocyanic acid. The mass of carbid-e and hydrocyanic acid is agitated. by

through an inlet 18 and withdrawn through an outlclat= 19. gaseousproduct withthe condensed: hydrocyanic acidy is delivered L by a pipe .2()ytoY a receiver 21` where any liquidV hydrocyanic acid separates and from which it isdelivered through a.r pipe 22jtoI .zi-supply receptacle*V 23 from vwhich the, liquid A hydrocyanic acidzpasses throughthepipe. 12 into tliereaction vessel.

The; gas. escaping: from. theA receiver 21 upwardly therein through a mass of inertmaterial 26 over Whichlthe, dilute solution of caustic soda flow-s continuously. The

caustic soda` absorbs anyl hydrocyanicy acid rema-ining\iny the acetylene,V which escapes through, anoutlet pipe 27 and may be conel veyed to any suitable storageA receptacle.4 The caustic soda is delivered from the tower throughi a.; pipel 28 forming a Seal into a receiverf-.29Jin,.Whicli. a isuitable supply of the solution. ismiaintained. From.` the receiver thei solutiony passes. 4through a. pipe 30,y to a pump. 31.` whicheturns it through a pipe` 32 to `a :spray 333 at' the top ofthe tower.

Waste'. pipeflffis connected tothe pipe 32.

andvalves 3,5 and-G-.are y provided toA permit the;5 discln ,rige-of the caustic. soda4 solution when it issuficiently. saturated with hydrocyanicf.,acidiy This solutioncanbe evaporated, to recover@V thergsodium. cyanide which is formedA5 therein.

Thefollowingexample will serve .to illustrate.: further theinaturebfthe invention which, however, isA no tgconlinedfto this eX.- ample, 1()i poundsA of. ammonium bromide wereplaced inthe reaction vessel withf).

pounds of redistilled hydrocyanic acid. Agitation of the mixture was started and 200. poundst ofground-:calcium carbide. were. During. .the addition ofi introduced slowly. the`v carbide'- the.y mass. was agitated.. continn uouslyC andcoldfwater was conducted `th rouoh thepjaclget,o fj the reaction apparatus. The reaction commenced *immediatelyv upon the addition .of the., carbide with considerable volencebutt was Controlled bvadjustmentofthe-rate of which the carbide was added' and by'A the; :circulation ofthe .cooling Water. in the jacket. Acetylene was given. offl freelyandatlris;acetylene, which carried.

lil@

a considerable` amount of hydrocyanic acid vapor, was assed through the condenser and cooled therein to condense the hydrocyanic acid vapors and toseparate the liquid thereby produced from the acetylene. When the reaction was substantially complet-e as indicated bythe fact that acetylene gas ceased to be evolved, waim water at approximately 60 C. was substituted for the cold water in the jacket. The circulation of warm water was continued until free hydrocyanic acid was vaporized and removed andthe product was then cooled and discharged.

The product thereby obtained was nearly white, very finely divided and showed by analysis a cyanogen content of 58.1 per cent. The yield was 93.8 per cent of the theoretical amount based upon the quantity of hydrocyanic acid employed.

The product dissolves quickly and completely in water except for such normal in soluble impurities as occur in the carbide employed. It is very susceptible to the action of the atmosphere, giving off hydrocyanic acid rapidly and copiously and leaving a powdery residue usually somewhat darker in color than the original material.

While the process as described is designed primarily to avoid the necessity of including water in the reaction between calcium carbide and hydrocyanic acid in order to promote the reaction, it is to be understood that strictly anhydrous hydrocyanic acid is not essential to the operation as described herein. Redistilled liquid hydrocyanic acid usually contains upward to about one-half of one per cent of water and this proportion of water is not detrimental to the reaction.

t The promoters as herein described replace the additional quantity of water which has been added or otherwise supplied heretofore for the purpose of accelerating thereaction between calcium carbide and hydrocyanic acid.

,[t is to be noted that the promoters such as ammonium bromide and the like, above mentioned, remain with and therefore become a constituent part of the finished prod uct, calcium cyanide. Although the pronioter constitutes but a small part (from l to 5%) of the finished product, we have found that its presence in the product has a beneficial e'ect in the following way. When calcium cyanide is exposed to the air in relatively thick layers for the purpose of liberating hydrocyanic acid therefrom, there is a tendency toward polymerization of a part of the hydrocyanic acid which thereby becomes ineffective. When, however, calcium cyanide, containing promoters such as ammonium bromide and the like is similarly exposed to the air, there is a marked decreased tendency toward polymerization. It is possible that this effect may be due to some extent at least to the absence of water as it is substantially eliminated from the reaction by theV use `ofthe described promoters. These promoters may therefore be regarded as having a beneficial effect on the product in that they act as stabilizers and decrease the tendency' toward polymerization of the liberated hydrocyanic acid, and there by constitute a valuable constituent of the product. Among the advantages of the invention as described are the reduction in the time required to complete the reaction. a substantially complete elimination of polymerized hydrocyanic acid in the finished product, increased eiiiciency with respect to the amount of hydrocyanic acid required, increased cyanogen content in the product, and a product of considerably lighter color and increased effectiveness than has been pro 85 duced by the reaction heretofore.

.The invention coinprehends the produc tion of cycnogen compounds of other metals, the carbdesof which may react with hydrocyanic :cid to produce such compounds.

As herein indicated, various types of apparatus may be used in conducting the reaction and the details of the operation may be modied without departing from the invention or sacrificing` any of the advantages thereof.

7e claim :m l. The process of preparing cyanogen compounds of the alkali-forming metals,

which comprises treating their carbides with 10 hydrocyanic acid in the presence of ammonium bromide.

2. The process of preparing a cyanogen compound of calcium, which comprises treating calcium carbide with hydrocyanic acid in the presence of ammonium bromide.

3. The method of preparing a cyanogen compound of the alkali-forming metals, which comprises treating their carbides with anhydrous liydrocyanic acid, and with a relatively small proportion of a promoter free from water and wateraforming components.

fl. The method of preparing a cyanogen compound of the alkali-forming metals, which comprises treating their carbides with anhydrous hydrocyanic acid, in the presence of a catalyst from the group comprising NI-LBr, NILCNS, CaBi-g, NHJ, ZnCL, ZnBrg, CGHSCOOH. d

5. The method of preparing a. cyanogen compound of the alkali-forming metals, which comprises treating their carbides with anhydrous hydrocyanic acid, in the presence of an NILR compound where Ris from the group comprising bromine, iodine and the thio-cyanate radical.

6. As an* article of manufacture, a composition of matter which contains calcium cyanide and a compound from the group Lemma;

Comprising'NHr,INHGNS, CaBrZ, NELL. 8. AS an article ofmanufaoture; a. com-- ZiiGl2ZnBr2,CGHSCOQH. ositiou of matter which oontainsfcalcium 7. Ags-.an article of manufacture, a.V comoyanido and ammonium bromide. 10 positionY of matter' which Contains calcium In testimony. Wliereo'l3 We uHiX our Signzu cyanide and. an NILR coii'ipound Where R tures.

is,l from the: group comprising bromine, ROBERT W. PGINDEXTER, JR. iodine, and the thiO-cyanate radical. WILLAM EARL OLBERG. 

